Ten people were killed in a northeastern Brazil shootout on Wednesday believed to be related to a long-running conflict over land rights.

According to police, nine men and a woman were killed in the incident.

Para Police Chief Joao Bosco said the violence occurred when police in the area on an unrelated investigation came under gunfire on the Santa Lucia Estate, located almost 1,000 kilometres (621 miles) from Belem, the capital of Para.

The officers retaliated but none were injured in the clash.

Para Secretary of Public Security Jeanot Jansen said the incident would be investigated.

Police did not give details on the original purpose of their patrol in the area, but the Pastoral Land Commission (CPT) said they were there to carry out “property re-integration.”

Disputes over property rights in Brazil are common. According to the CPT, 61 people were killed in land conflicts in Brazil last year.